Six-roller-type wave generators for wave gear devices are known in the art. Wave generators of this type are provided with six rollers for causing the flexible externally toothed gear of the wave gear device to be flexed into an appropriate ellipse-like shape. One pair of these rollers is arranged in symmetrical positions on the long axis of the ellipse-like shape, and the remaining two pairs of rollers are arranged so as to be in linear symmetry in relation to the long axis between the long axis and short axis of the ellipse-like shape. This type of wave generator is disclosed in FIG. 3 of Patent Document 1.